They've always done it at my store down in Houston. It saves our store over a thousand bucks a month, which means more from the budget to put towards hours and hiring more people. If it also saves electricity, then kudos to them.
The lights dim at 10 PM. Also they dim some in the day because we have skylights. Also they took the lights out of the Big K Machine. And they started pulling the doors down on both the trailers they stay at 2 of the doors. That keeps the backroom alot cooler. Then most of the time the spotlight is left on that shines in the trailer when one is dark.